Bài tập java cơ bản (P4 - xâu)

Bài 01
/**
*Cho truoc 1 xau ky tu la ho ten nguoi day du nhung khi nhap co the thua mot so dau cach.
*Hay xoa di cac dau cach thua va in ra ho ten chinh xac.
*/
public class String01 {
       public static void main(String[] args) {
              String S = new String (" Nguyen Thi Binh ");
              String S1,S2 = new String ();
              S=S.trim();
              for (int k=0; k<S.length();k++)
              {
                     S1=S.substring(k,k+1);
                     if (S1.equals(" "))
                     {
                           S1=S.substring(k+1,k+2);
                           if (S1.equals(" "))
                                  continue;
                           else S2=S2+S.substring(k,k+1);
                     }
                     else S2=S2+S1;
              }
              System.out.print(S2);
       }
}
Kết quả
Pepsi Milo Ovantine
Process completed.
Bài 02
/**
*Cho truoc xau ky tu bat ky. Hay dem xem trong xau co bao nhieu lan xuat hien xau con “abc”.
*/
public class String02 {
       public static void main(String[] args) {
              String S = new String ("abc def ab cdfg abcabc");
              String S1= new String ();
              int dem=0;
              for (int k=0;k<S.length()-2;k++)
              {
                     S1= S.substring(k,k+3);
                     if(S1.equals("abc"))
                           dem++;
              }
              System.out.print(dem);
       }
}
Kết quả
3
Process completed.
Bài 03
/**
* Cho truoc 1 xau ky tu la ho ten nguoi day du, hay tach ra phan ten cua nguoi nay.
*/
public class String03 {
       public static void main(String[] args) {
              String S = new String (" Nguyen Van An ");
              String S1 = new String ();
              S=S.trim();
              int k;
              for (k=S.length()-1;k>=0;k--)
              {
                     S1=S.substring(k,k+1);
                     if(S1.equals(" "))
                           break;
              }
              System.out.print("Ten cua nguoi do la:"+S.substring(k+1));
       }
}
Kết quả
Ten cua nguoi do la:An
Process completed.
Bài 04
/**
*Cho truoc 1 xau ky tu la 1 ho ten nguoi day du, hay tach ra phan ho cua nguoi nay
*/
public class String04 {
       public static void main(String[] args) {
              String S = new String (" Nguyen Van An ");
              String S1 = new String ();
              S=S.trim();
              int k;
              for (k=0;k<=S.length();k++)
              {
                     S1=S.substring(k,k+1);
                     if(S1.equals(" "))
                           break;
              }
              System.out.print("Ho cua nguoi do la:"+S.substring(0,k));
       }
}
Kết quả
Ho cua nguoi do la:Nguyen
Process completed.
Bài 05
/**
*Cho 1 xau ky tu bao gom toan cac ky tu 0, 1. Hay bien doi xau nay theo cach 0 -> 1, 1->0 va in ra ket
qua.
*/
public class String05 {
       public static void main(String[] args) {
              String S = new String ("010001110001100");
              String S1= new String ();
              String S2= new String ();
              for (int k=0;k<S.length();k++)
              {
                     S1=S.substring(k,k+1);
                     if (S1.equals("0"))
                           S1="1";
                     else
                           S1="0";
                     S2=S2+S1;
              }
              System.out.print(S2);
       }
}
Kêt quả
101110001110011
Process completed.
Bài 06
/**
*Cho truoc xau ky tu S, in ra xau S1 nguoc lai xau S.
*/
public class String06 {
       public static void main(String[] args) {
              String S,S1,S2= new String ();
              S="1234567890";
              for ( int k=S.length()-1;k>=0;k--)
              {
                     S1=S.substring(k,k+1);
                     S2=S2+S1;
              }
              System.out.print(S2);
       }
}
Kết quả
0987654321
Process completed.
Bài 07
/**
* Cho truoc xau ky tu S. Hay bien doi S theo quy tac sau: chu so thi bien thanh “$” con cac ky tu khac
giu nguyen.
**/
public class String07 {
       public static void main(String[] args) {
       String S = new String ("12a3456b78 c 90");
       String [] X= {"0","1","2","3","4","5","6","7","8","9"};
       String S1= new String ();
       String S2= new String ();
       for ( int k=0;k<S.length();k++)
       {
              S1=S.substring(k,k+1);
              for (int j=0;j<10;j++)
                     if (S1.equals(X[j]))
                     {
                           S1="$";
                           break;
                     }
                     S2=S2+S1;
                     }
              System.out.print(S2);
       }
}
Kết quả
$$a$$$$b$$ c $$
Process completed.
Bài 08
/**
*Cho truoc 2 xau ky tu S1, S2. Hay dem xem xau S1 xuat hien trong S2 tai bao nhieu vi tri.
*/
public class String08 {
       public static void main(String[] args) {
       String S1= new String ("abc def ghj abc ab c");
       String S2= new String ("abc");
       String S3= new String();
       int dem=0;
              for (int k=0;k<S1.length()-S2.length();k++)
              {
                     S3=S1.substring(k,k+S2.length());
                     if (S3.equals(S2))
                           dem++;
              }
              System.out.print(dem);
       }
}
Kết quả
2
Process completed.
Bài 09
/**
*Cho xau S va 2 chi so i, j. Hay doi cho 2 vi tri i, j trong S.
*/
public class String09 {
       public static void main(String[] args) {
       String S= new String ("0123456789");
       String S1,S2 = new String();
       int i=3,j=8;
       int N=S.length();
       for (int k=0;k<N;k++)
       {
              S1= S.substring(k,k+1);
              if ((k!=i) && (k!=j))
                     S2=S2+S1;
              if (k==i)
                     S2=S2+S.substring(j,j+1);
              if (k==j)
                     S2=S2+S.substring(i,i+1);
              }
              System.out.print(S2);
       }
}
Kết quả
0128456739
Process completed.
Bài 10
/**
*Cho mang xau ky tu S1, S2… Sn. Hay tim va in ra phan tu xau co do dai lon nhat.
*/
public class String10 {
       public static void main(String[] args) {
              String [] S = {"Hehe", "hahaha", "hihihihi"};
              int max=0;
              for (int k=0;k<3;k++)
              {
                     if (max<S[k].length())
                           max=S[k].length();
              }
              for (int k=0;k<3;k++)
              {
                     if (S[k].length()==max)
                     System.out.print(S[k]);
              }
       }
}
Kết quả
hihihihi
Process completed.
Bài 11
/**
*Cho danh sach ho ten day du hoc sinh. Hay dem xem co bao nhieu ban ten “An”.
*/
public class String11 {
       public static void main(String[] args) {
              String [] ds = {" Nguyen Van An","Nguyen Thi Binh ", "Le Van Lan ","Le An "};
              int dem=0;
              for(int k=0;k<4;k++)
                     {
                           ds[k]=ds[k].trim();
                           int N=ds[k].length();
                           String S1=ds[k].substring(N-2);
                           if (S1.equals("An"))
                           dem++;
                     }
              System.out.print(dem);
       }
}
Kết quả
2
Process completed.
Bài 12
/**
*Cho danh sach ho ten day du hoc sinh. Hay dem xem co bao nhieu ban co phan dem la “Thi”.
*/
public class String12 {
       public static void main(String[] args) {
              String [] dshs = {" Nguyen Thi Lan", "Nguyen Thi Binh ","Le Van Lan "};
              int dem=0;
              for (int k=0;k<3;k++)
              {
                     dshs[k]=dshs[k].trim();
                     String S1= new String ();
                     int N= dshs[k].length();
                     int i,j;
                     for (i=0;i<N;i++)
                     {
                           S1=dshs[k].substring(i,i+1);
                           if(S1.equals(" "))
                           break;
                     }
                     for (j=N-1;j>=0;j--)
                     {
                           S1=dshs[k].substring(j,j+1);
                           if(S1.equals(" "))
                                  break;
                     }
                     S1=dshs[k].substring(i+1,j);
                     if(S1.equals("Thi"))
                           dem++;
              }
              System.out.print(dem);
       }
}
Kết quả
2
Process completed.
Bài 13
/**
*Cho danh sach ho ten day du hoc sinh. Hay dem xem co bao nhieu ban co ten bat dau bang chu “H”.
*/
Cách 1
public class String13 {
       public static void main(String[] args) {
              String [] ds={"Nguyen Thi Binh "," Tran Binh Minh "," Nguyen Thi Hoa "};
              int i;
              int dem=0;
              String S= new String();
              for(int k=0;k<3;k++)
              {
                     ds[k]=ds[k].trim();
                     int N=ds[k].length();
                     for (i=N-1;i>=0;i--)
                     {
                           S=ds[k].substring(i,i+1);
                           if (S.equals(" "))
                                  break;
                     }
                     S=ds[k].substring(i+1,i+2);
                     if(S.equals("H"))
                           dem++;
              }
              System.out.print(dem);
       }
}
Cách 2
public class String13_2 {
       public static void main(String[] args) {
              String [] ds={"Nguyen Thi Binh "," Tran Binh Minh "," Nguyen Thi Hoa "};
              int i;
              int dem=0;
              for(int k=0;k<3;k++)
              {
                     ds[k]=ds[k].trim();
                     int N=ds[k].length();
                     for (i=N-2;i>=0;i--)
                     {
                           String S=ds[k].substring(i,i+2);
                           if (S.endsWith("H") && S.startsWith(" "))
                           {
                                  dem++;
                                  break;
                           }
                     }
              }
              System.out.print(dem);
       }
}
Kết quả
1
Process completed.
Bài 15
/**
*Day xau ki tu S1,S2... duoc cho theo quy tac sau
*S1="1111100000", Sk thu duoc tu Sk-1 bang cach thay doi cho lan luot cac vi tri
*1-2;2-3;3-4;4-5;5-6;6-7;7-8;8-9;9-10
*Cho truoc so tu nhien N , hay in ra xau Sn
*/
public class String15 {
       public static void main(String[] args) {
              String S = new String ("0123456789");
              String S1 = new String ();
              int N=2;
              int k,dem=0;
              int L=S.length();
              while (dem<N)
              {
                     for (k=1;k<L;k++)
                     S1=S1+S.charAt(k);
                     S1=S1+S.charAt(0);
                     S=S1;
                     S1="";
                     dem++;
              }
              System.out.print(S);
       }
}
Kết quả
2345678901
24
Process completed.
Bài 16
/**
*Cho truoc 2 xau ki tu S1,S2.hay chen xau S1 vao giua xau S2 va in ra ket qua
*/
public class String16 {
       public static void main(String[] args) {
              String S2= new String ("123456789");
              String S1=new String("abcdefg");
              String S3=new String();
              int N=S2.length();
              int k;
              if (N%2==0) k=N/2;
              else
              k=(N+1)/2;
              S3=S2.substring(0,k);
              S3=S3+S1;
              S3=S3+S2.substring(k);
              System.out.print(S3);
       }
}
Kết quả
12345abcdefg6789
Process completed.
Bài 17
/**
*Cho truoc 2 xau S1,S2. Hay xet xem xau S1 o phai la xau con cua S2 neu xoa bo vai ky tu cua xau S2
duoc xau S1
*/
public class String17 {
       public static void main(String[] args) {
              String S1= new String ("abcdefg");
              String S2= new String ("abc3456defg789");
              int x=0,j=0,dem=0,k;
              int N2=S2.length();
              int N1=S1.length();
              while (j<N1)
              {
                     k=x;
                     while (k< N2)
                     {
                           if (S2.charAt(k)==S1.charAt(j))
                           {
                                  dem++;
                                  x=k;
                                  break;
                           }
                           else k++;
                     }
                     j++;
              }
              if (dem==N1)
                     System.out.print("S1 la chuoi con cua S2 ");
              else
                     System.out.print("S1 khong phai la chuoi con cua S2");
       }
}
Kết quả
S1 la chuoi con cua S2
Process completed

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