java8-tutorial/src/com/winterbe/java8/Maps1.java at master · alex-zhh/java8-tutorial · GitHub

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package com.winterbe.java8;

import java.util.HashMap;

import java.util.Map;

/**

* @author Benjamin Winterberg

public class Maps1 {

public static void main(String[] args) {

Map<Integer, String> map = new HashMap<>();

for (int i = 0; i < 10; i++) {

map.putIfAbsent(i, "val" + i);

}

map.forEach((id, val) -> System.out.println(val));

map.computeIfPresent(3, (num, val) -> val + num);

System.out.println(map.get(3)); // val33

map.computeIfPresent(9, (num, val) -> null);

System.out.println(map.containsKey(9)); // false

map.computeIfAbsent(23, num -> "val" + num);

System.out.println(map.containsKey(23)); // true

map.computeIfAbsent(3, num -> "bam");

System.out.println(map.get(3)); // val33

System.out.println(map.getOrDefault(42, "not found")); // not found

map.remove(3, "val3");

System.out.println(map.get(3)); // val33

map.remove(3, "val33");

System.out.println(map.get(3)); // null

map.merge(9, "val9", (value, newValue) -> value.concat(newValue));

System.out.println(map.get(9)); // val9

map.merge(9, "concat", (value, newValue) -> value.concat(newValue));

System.out.println(map.get(9)); // val9concat

}

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