| Method | interpretative statement |
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char charAt(int index)
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Returns the index character in the string
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boolean equals(String other)
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Returns true if the string is equal to another; otherwise, returns false.
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boolean equalsIgnoreCase(String other)
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Returns true if the string is equal to another (case ignored); otherwise, returns false.
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int indexOf(String str)
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Returns the index position of the first substring str in the string from scratch. If the substring str is not found, - 1 is returned.
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lastIndexOf()
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Returns the index position of the first substring str in the string from the end. If the substring str is not found, - 1 is returned.
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int length()
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Returns the length of the string.
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String replace(char oldChar,char newChar)
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Returns a new string generated by replacing all oldchars that appear in the string with newChar.
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boolean startsWith(String prefix)
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Returns true if the string starts with prefix.
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boolean endsWith(String prefix)
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Returns true if the string ends in prefix.
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String substring(int beginIndex)
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Returns a new string from the original string beginIndex to the end of the string.
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String substring(int beginIndex,int endIndex)
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Returns a new string containing all characters from the original string beginIndex to the end of the string or endIndex-1.
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String toLowerCase()
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Returns a new string that changes all uppercase letters in the original string to lowercase letters.
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String toUpperCase()
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Returns a new string that changes all lowercase letters in the original string to uppercase letters.
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String trim()
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Returns a new string that removes spaces at the beginning and end of the original string
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Code test:
package demo4; public class StringTest { public static void main(String[] args) { String s="abcd"; String s1=new String("abcd"); System.out.println(s==s1); // Address comparison results false System.out.println(s.equals(s1));//Value comparison results true System.out.println(s.substring(1));//Intercept from where subscript is 1 System.out.println(s.substring(1,3));//Intercept from subscript 1 to the end of subscript 3 excluding 3 String value="abcdefjf"; System.out.println(value.charAt(3));//Index 3 is d System.out.println(value.replace("fj","&"));//hold fj replace with& System.out.println(value.indexOf("e"));//Character string e Index position 4 of System.out.println(value.indexOf("BB"));//Include this string, not return-1 System.out.println(value.lastIndexOf("f"));//Character string f Last position 7 System.out.println(value.startsWith("a"));//Whether to use a Start true System.out.println(value.endsWith("f"));//Whether to use f Ending String value1=" I love you !"; System.out.println(value1.trim());//Remove all spaces System.out.println(value1.replace(" ",""));//Remove all spaces System.out.println(value1.toUpperCase());//String to uppercase System.out.println(value1.toLowerCase());//String to lowercase } }
StringBuffer and StringBuilder
- List of common methods:
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Overloaded public StringBuilder append( )Method to add a character sequence to the StringBuilder object, still returning its own object.
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Method public StringBuilder delete(int start,int end) can delete a character sequence from start to end-1, and still return its own object.
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Method public StringBuilder deleteCharAt(int index) removes the char at the specified location of this sequence and still returns its own object.
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Overloaded public StringBuilder insert( )Method can insert a character sequence for the StringBuilder object at a specified location and still return its own object.
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The method public StringBuilder reverse() is used to reverse the character sequence and still return its own object.
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Method public String toString() returns the string representation of the data in this sequence.
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Methods with similar meaning to String class:
public int indexOf(String str)
public int indexOf(String str,int fromIndex)
public String substring(int start)
public String substring(int start,int end)
public int length()
char charAt(int index)
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String: immutable character sequence. A kind of
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StringBuffer: variable character sequence, thread safe, but inefficient. A kind of
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StringBuilder: variable character sequence, unsafe thread, but high efficiency (commonly used).
package com.sxt.demo; public class TestString { public static void main(String[] args) { String s="abCde "; System.out.println(s.charAt(3));//Index 3 is d System.out.println(s.toLowerCase());//Change this string to lowercase System.out.println(s.toUpperCase());//Change this string to uppercase System.out.println(s.substring(0,3));//Intercept 0-3 Index string System.out.println(s.replace("d","o"));//replace System.out.println(s.trim());//Remove spaces System.out.println(s.lastIndexOf("e"));//The last one e Index locations that appear System.out.println(s.indexOf(3));//Whether the string contains 3, not return-1 System.out.println(s.endsWith(" "));//Whether to end with a space System.out.println(s.startsWith("a"));//Whether to use a Start StringBuilder value=new StringBuilder(); value.append("I am"); value.append("One"); value.append("Cute guy");//Append character meaning System.out.println(value); for(int i=1;i<=10;i++){ value.append(i); } System.out.println(value); StringBuffer a=new StringBuffer("Happy forever"); System.out.println(a.delete(4,6));//Index 4-6 Delete where System.out.println(a.insert(0,"I"));//Insert me at index 0 System.out.println(a.insert(1,"Meeting"));//Insert at index 1 System.out.println(a.reverse());//Reverse string } }