5. String

String is used to hold character sequences. We do not have to use new to create a new instance of this class.

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toUpperCase converts everything to uppercase.

  // *** 1. Start (toUpperCase)
  String s1 = "test";
  String s2 = s1.toUpperCase();
  System.out.println("s2 = " + s2);
  // *** 1. End

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toLowercase converts everything to lowercase.

  // *** 2. Start (to toLowerCase)
  String s3 = "TEST";
  String s4 = s3.toLowerCase();
  System.out.println("s4 = " + s4);
  // *** 2. End

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indexOf finds index of substring within a string. If the substring is not found in string, it returns -1. contains indicates if the substring is inside the string.

  // *** 3. Start (index of, contains)
  String s5 = "abcdefghi jklmnopq";
  int locOfi = s5.indexOf('i');
  System.out.println("locOfi = " + locOfi);
  boolean conLetti = s5.contains("i");
  System.out.println("conLetti = " + conLetti);
  // *** 3. End

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Two strings can be checked for equality with equals. For a equality check that ignores case, use equalsIgnoreCase.

  // *** 4. Start (equals)
  String s6 = "president";
  String s7 = "president";
  boolean b1 = s6.equals(s7);
  boolean b2 = s6.equals("President");
  boolean b3 = s6.equalsIgnoreCase("President");
  System.out.println("b1 = " + b1 +
               "\tb2 = " + b2 +
               "\tb3 = " + b3);
  // *** 4. End

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toCharArray converts a string to character array. The method length() finds length of string, while the field length does the same for character arrays.

  // *** 5. Start (String to char[], length)
  String s8 = "Time";
  char[] cArr = s8.toCharArray();
  System.out.println(cArr);
  int lenOfs8 = s8.length();
  int lenOfcArr = cArr.length;
  System.out.println("lenOfs8 = " + lenOfs8 +
             "\tlenOfcArr = " + lenOfcArr );
  // *** 5. End

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package com.javaAndroid.ex5;

public class Ex5 {
 public static void main(String[] args) {
  // *** 1. Start (toUpperCase)
  String s1 = "test";
  String s2 = s1.toUpperCase();
  System.out.println("s2 = " + s2);
  // *** 1. End
  // *** 2. Start (to toLowerCase)
  String s3 = "TEST";
  String s4 = s3.toLowerCase();
  System.out.println("s4 = " + s4);
  // *** 2. End
  // *** 3. Start (index of, contains)
  String s5 = "abcdefghi jklmnopq";
  int locOfi = s5.indexOf('i');
  System.out.println("locOfi = " + locOfi);
  boolean conLetti = s5.contains("i");
  System.out.println("conLetti = " + conLetti);
  // *** 3. End
  // *** 4. Start (equals)
  String s6 = "president";
  String s7 = "president";
  boolean b1 = s6.equals(s7);
  boolean b2 = s6.equals("President");
  boolean b3 = s6.equalsIgnoreCase("President");
  System.out.println("b1 = " + b1 +
               "\tb2 = " + b2 +
               "\tb3 = " + b3);
  // *** 4. End
  // *** 5. Start (String to char[], length)
  String s8 = "Time";
  char[] cArr = s8.toCharArray();
  System.out.println(cArr);
  int lenOfs8 = s8.length();
  int lenOfcArr = cArr.length;
  System.out.println("lenOfs8 = " + lenOfs8 +
             "\tlenOfcArr = " + lenOfcArr );
  // *** 5. End
 }
}

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